The present invention relates to a device for positioning components within endoscopic systems, having a hermetically sealed housing, an outer ring element mounted to rotate about the outer side of said housing and carrying on its circumference at least one outer magnet, another inner ring element mounted inside said housing and carrying at least one inner magnet, said magnets being arranged such that any rotation of said outer ring element has the effect to move said at least one inner magnet by magnetic coupling, such movement serving the purpose to position the respective components.
A device of this kind has been known from DE 195 21 654 A1.
The term positioning as used in the context of the present invention includes axial displacement and/or circumferential displacement to bring the components into a desired position.
The term components includes, for example, optical components such as lenses in an optical head of an endoscope. An axial displacement of the system serves for focusing or adjusting the optical system. The term components also includes mechanical components, which are to be swung into and out of an optical system, such as filters, diaphragms or the like. The positioning device may be handled from the proximal end of the endoscopic system, while the component to be moved may be arranged also at the distal end and may be connected with the positioning device via some linkage.
The term endoscopic systems as used in the present invention is meant to describe endoscopes and also endoscopic camera systems.
The term hermetically sealed housing as used in the present invention is meant to describe a housing sufficiently tight to allow it to be autoclaved, for example, without any risk of humidity or liquids, i.e. contaminations, penetrating into the interior of the housing as a result of the extreme temperature variations encountered. The outer magnets of the outer ring element arranged around the outer side of the tight housing interact in the way of a magnetic coupling with the inner magnets of the inner ring element arranged inside the tight housing.
In the case of the known optical device mentioned at the outset the inner magnet is received in a helically shaped slot of a sleeve mounted stationarily inside the tight housing. A lens mount, carrying the lenses of a lens group, is mounted for axial displacement and rotation inside the sleeve. The inner magnet, being configured as a circular magnet, engages a radial blind bore provided on the outer circumference of the lens mount.
The magnet of the outer rotatable ring element is configured as a rectangular magnet that interacts with the circular magnet, i.e. is arranged substantially opposite the latter.
Rotation of the outer ring element together with the rectangular magnet causes the inner circular magnet to be rotated simultaneously. Since the circular element is received in a helically shaped slot in the sleeve, it also moves in axial direction.
Consequently, the rectangular magnet located on the outer ring must have an axial extension that corresponds to the maximum axial displacement of the inner circular magnet as it moves along the helically shaped slot in the sleeve.
The fact that the circular magnet engages a radial blind bore on the outer side of the lens mount results in the latter being axially displaced in response to the axial advance motion of the circular magnet.
This configuration is connected with the disadvantage that due to the axial mobility of the inner magnet the outer ring magnet must have a very long axial extension, i.e. a big overall size, which leads to bulky and large structures. The magnet in the outer ring being relatively big, it emits magnetic stray fields to the outside which may interfere with systems that work with electron beams, such as monitors or endoscopic cameras, or the like. In addition, the inner circular magnet is mechanically connected with two different components, namely the outer stationary sleeve with the helically shaped slot, and the blind bore in the inner mount of the optical system. In order to ensure jam-free operation, it is necessary to use precisely manufactured parts and also to provide a certain play with the result that especially reversing movements will lead to jerky movements with changes in adjustment of the optical system.
U.S. Pat. No. 5,359,992 describes a device for positioning components within endoscopic systems, where two diametrically opposite helically shaped slots are provided in the outer ring element in which diametrically opposite circular magnets are inserted. The circular magnets engage an axial directed recess in the outer side of a sleeve arranged in the ring. Rotation of the outer ring thus causes the outer magnet to move in axial direction. Inside the closed section, there are provided corresponding diametrically opposite magnets which follow the movements of the outer magnet, thereby effecting the coupling action. The inner set element, with the inner magnets, is not guided mechanically so that in the event the inner element should get out of the magnetic field of the outer magnet, due to a shock or some other impact, it can be moved toward and backward, and can be rotated inside the housing. In order to reestablish the proper function, the endoscope then has to be pivoted until the interaction between the outer and inner magnets has been reestablished.
A similar structure has been known from DE 88 10 044 U1, where a magnet arranged on the inner side of the outer ring interacts with an inner magnet of very long extension.
The outer magnet is moved in axial direction thereby entraining the inner magnet and effecting the coupling effect.
A telescope functioning according to that basic lens-adjusting principle has been known from German Patent Specification No. 970 298. Here again, there is a risk that mechanical shocks may bring the inner magnet out of magnetic interaction with the outer magnet.